Vapor electric device



March 18, 1941. w. M. BRUBAKER 2,235,396

VAPOR ELECTRIC DEVICE Filed Feb 16,1940 3 Sheets-Sheet l WITNESSES: INVENTOR wwm Wilson M Brubalser 9% W U; Mm

ATTORN EY March 18, 1941. w M BRUBAKER 2,235,396

VAPOR ELECTRIC DEVICE Filed Feb. 16, 1940 5 Sheets-Sheet 2 Fiy 3i vvvv WITNESSES: INVENTOR Wilson M. Brubaken M W 6 J i JMw ATTORNEY March 18, 1941. w. M. BRUBAKER VAPOR ELECTRIC DEVICE Filed Feb. 16, 1940 3 Sheets-Sheet 3 OUlI'OQOtIIUOQIO! INVENTOR Wilson M Brwbak n WITNESSES: QTAHMLWJWL BY J, KW

ATTORNEY Patented Mar. 18, 1941 UNITED STATES PATENT OFFICE VAPOR ELECTRIC DEVICE Pennsylvania Application February 1 5 Claims.

My invention relates to a vapor-electric converter and, particularly, to means for controlling the condensation of the excess vapor in a mercury arc rectifier.

In the operation of vapor-electric devices, such as mercury arc valves, it has long been known that the presence of excessive cathode vapor produces a tendency to arc back in the valve device. It has recently been discovered that the heretofore supposed condensing ability of the cooling condensing surfaces of vapor electric devices was much less than was supposed. In fact, the best heretofore produced devices had a condensing efliciency of less than one-tenth of the theoretical condensing ability of such surface. It has been discovered that this condensing efiiciency could be greatly improved by causing a positive ion bombardment of the condensing surfaces. This was accomplished, as shown in application Serial No. 264,936, filed March 30, 1939, of Joseph Slepian, et al. and assigned to the same assignee as the present application. While the bombardment of the condensing surfaces as disclosed in the prior filed application produced the necessary low vapor pressure, the expected reduction in arc back probability did not materialize. Further, investigation has shown that when the condensing surface is maintained at a negative potential during the inverse or negative half cycle there is a tendency for incipient cathode spots to form on the condensing surface, producing a blast of ionization which tended to reduce the reliability against arc back.

It is an object of the present invention to provide a system by which the energization of the condensing surface is maintained only during the interval during which a current carrying arc is maintained in the vapor electric device.

It is a further object of my invention to provide circuit means which are automatically operative to apply negative potential to the condensing surfaces only during the interval during which the valve is carrying current.

Other objects and advantages of my invention will be apparent from the following detailed description taken in conjunction with the accomp nyi g drawings, in which:

Figure 1 is a schematic illustration of a vapor electric conversion system utilizing simple means for securing the application of the negative potential to the condensing surface;

Fig. 2 is a view similar to Fig. 1 showing a mod ified form;

Fig. 3 is a further modification showing means 6, 1940, Serial No. 319,277

for shortening the duration of the application of the potential to the condensing surface;

Fig. 4 is a further modification showing means responsive to current flow for charging the condensing surface;

Fig. 5 is a modification similar to Fig. 4 show ing a means for controlling the duration of the application of charging potential to the condensing surface; and

Fig. 6 is a further modification according to my invention.

In the illustrative embodiment of my invention according to Fig. l, the system comprises a plurality of vapor electric devices, such as ignitron valves, each valve comprising an anode I and a vaporizable reconstructing cathode 2 of such material as mercury, mercury amalgam, or galium, the whole being contained within an evacuated container 3, the side wall 4 of which is preferably insulated from the anode and cathode 2 and cooled by suitable means such as the cooling coil 5 suitably connected to the exterior thereof for providing a cooled condensing surface.

The anodes l of the valves are successively periodically energized from a suitable power source 6, preferably by means of a suitable transformer device 1 so that direct current is supplied to the load circuit 8.

In order to secure a source of negative potential for the condensing surfaces 4, the condensing surface 4 is connected through a suitable unidirectional device 9 to a point IU of opposite po tential in the converter transformer 1. If the transformer potential is of a suitable low value, this connection may obviously be made directly to the anode connection of opposite polarity and the current controlled by means of a suitable resistor II in the circuit for the condensing sur face 4.

In the event that the transformer potential is of too high a value to be successfully applied to the condensing surface, and it is inconvenient to provide a proper tap in the main transformer l, a suitable auxiliary charging transformer i2 may be provided as shown in Fig. 2.

In order to reduce the size of the auxiliary transformer I2 and the power required thereby, it is desirable to connect the opposite ends of the auxiliary transformer secondary Hi to the cathode circuit so that the entire potential of the auxiliary transformer I2 is available for application to the condensing surface, suitable resistors l4 being provided for controlling the amount of current flow and suitable unidirectional conductors it, which may be of any type of auxiliary valves, such as copper-oxide rectifiers, are utilized for determining the application according to the potential of the transformer. This auxiliary transformer must, of course, be synchronized with the main power supply, and I prefer to do this by directly connecting the auxiliary transformer in opposite polarity to the power source 6 supplying the main transformer I.

In certain applications the period of conductivity of the valves is less than a full half cycle. In order to secure application of the charging potential to the condensing surface 4 only for the period not exceeding the conducting interval, a suitable biasing potential l6 may be inserted between the auxiliary transformer l2 and the cathodes of the valves, as disclosed in Fig. 3.

Since the use of the positive bias l6 might conceivably raise the condensing surface to a potential which is positive with respect to the cathode, a suitable high resistance connection I! may be applied between the cathode and the condensing surface so that the voltage drop across the resistor 17 will be available to maintain the condensing surface 4 at a suitable negative potential with respect to the cathode, suitable unidirectional conductors it being provided between the auxiliary power source I2 and the condensing surface 4 to determine the polarity of the potential applied to the condensing surface.

In control rectifiers where the arc period may be considerably less than a full half cycle or in a device feeding reactive loads, it is desirable to make the application of the negative potential to the condensing surface automatically synchronize with the duration of the arc in the valve.

In the modification according to Fig. 4, I have shown such an automatic circuit comprising a series transformer 20 similar to a current transformer connected in the current lead of the vapor electric valve. The periodic flow of current through this conductor produces potential impulses of opposite polarity in the auxiliary transformer 20. I prefer to so connect the auxiliary transformer 20 that the potential generated during the time when the current through the valve is increasing is connected to apply negative potential to the condensing surface 4. This is secured by connecting the free ends of the transformer 20 across a suitable resistance 2!, the positive terminal of the resistor 2| being connected to the cathode of the valve, and the negative terminal of the resistor 21 being connected to the condensing surface 4. In order to prevent the application of the positive half wave to the condensing surface 4, a suitable low resistance unidirectional device 22 is connected in parallel with the resistor 2|.

If the application of inverse potential supplied by the auxiliary transformer 20 is of too short a duration, this duration may be increased by providing a condenser 23 in parallel with the resistor and a suitable unidirectional device 24 for preventing discharge of the condenser 23 through the windings of the auxiliary transformer 20, as shown in the modification according to Fig. 5.

In the modification according to Fig. 6, the auxiliary transformer 30 is connected in series with the current connection from the cathodes 2 of two valves of opposite conductivity. The alternate flow of current from the two valves then produces an alternating current impulse in the secondary of the auxiliary transformer 30, which alternating current may be conveniently connected to the condensing surface 4 by means of suitable unidirectional conductors 3|.

While for purposes of illustration, I have shown and described specific modifications of my invention, it is apparent that many changes and modi fications may be made therein without departing from the true spirit of the invention or the scope of the appended claims.

I claim as my invention:

1. A valve type converter system comprising a source of alternating current, a consuming circuit, a valve including an anode and a cathode for controlling the flow of current to said consuming circuit, a metallic condensing surface in said valve, said condensing surface being insulated from said anode and said cathode, transformer means responsive to current flow through said valve for applying to said condensing surface a potential negative with respect to the cathode.

2. A valve type converter system comprising a source of alternating current, a consuming circuit, a valve including an anode and a cathode for controlling the flow of current to said consuming circuit, a metallic condensing surface in said valve, said condensing surface being insulated from said anode and said cathode, transformer means responsive to current flow through said valve for applying to said condensing surface a potential negative with respect to the cathode, and means for controlling the time interval of the application of said potential.

3. A valve type vapor electric converter comprising a plurality of substantially independent vapor electric valves, each valve including an anode, a vaporizing cathode, a metallic condensing surface in proximity to the space between the anode and cathode, said condensing surface being insulated from said anode and cathode transformer means for successively supplying an arc in the valves of the converter, auxiliary transformer means for producing a potential which is negative to the cathode and means for applying said potential to the condensing surface of the valve carrying an are.

4. An electric current conversion system comprising a source of current, a load circuit, electric valve means for controlling the flow of current from said source to said load circuit, a conducting condensing surface associated in insulated relation with said valve means, a transformer energized by increase of current flow through said valve means for applying a negative potential to said condensing surface, and means for suppressing the positive potential output of said transformer means.

5. An electric current conversion system comprising a source of current, a load circuit, electric valve means for controlling the flow of current from said source .to said load circuit, a conducting condensing surface associated in insulated relation with said valve means, a transformer energized by increase of current flow through said valve means for applying a negative potential to said condensing surface, and a unidirectional conductor in shunt with said transformer to bypass the positive potential produced thereby.

WILSON M. BRUBAKER. 

